Techniques for automatically extracting a specific region from an image are utilized in various fields such as a medical field, an image processing field, a production control field, and an environment recognition field. An image segmentation technique is known as one of these techniques (see, PTL 1, PTL 2 and NPL 1, for example).
In the technique disclosed in PTL 1, a designation of a region (hereinafter, referred to as a “designation region”) which designates a region to be extracted (hereinafter, referred to as a “target region”) is received from a user. The target region is, for example, a foreground portion of an image, while the designation region is, for example, a portion including a trajectory of the drag operation performed by the user on the image. PTL 1 discloses a technique for extracting as a target region a range which is continuous with the designation region and in which a difference between pixel values of adjacent pixels is equal to or smaller than a predetermined threshold.
PTL 2 discloses a technique for extracting as a target region a region in which a difference in a distance between the region and a designation region is equal to or smaller than a predetermined threshold. Here, the distance refers to a distance component from a reference position such as a viewpoint of a camera to a subject.
NPL 1 discloses a technique called a graph cut method, in which a target region is extracted based on similarities of a pixel value component and a distance component between the region and a designation region and connectivity of pixel values between adjacent pixels.
The related arts mentioned above enable a target region to be extracted from an image only by designation of part of the target region without designation of the entire target region.